ABSTRACT ? ARTFL LEFFTDS Longitudinal FTLD: CLINICAL CORE The ARTFL LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) protocol represents an expanded and integrated international research consortium involving seven cores and two projects; ALLFTD is designed to substantially and comprehensively increase the amount of longitudinal data, numbers of biospecimen samples and MRI scans that are publicly available for research in FTLD, to ultimately foster development of disease-modifying therapies. Previously, the Advancement of Research and Treatment in Frontotemporal Lobar Degeneration (ARTFL; U54 NS092089) and Longitudinal Evaluation of Familial Frontotemporal Dementia Subjects (LEFFTDS; U01 AG045390) protocols collectively enrolled >1100 participants at 18 sites, including >380 members of families affected by MAPT, GRN and C9orf72 mutations (surpassing the original LEFFTDS target of 300), with the remaining participants being sporadic FTLD patients enrolled through ARTFL. Detailed clinical and neuropsychological data, including (but not limited to) the National Alzheimer's Coordinating Center (NACC) Uniform Data Set Version 3 and FTLD Module has been completed, with almost 1200 data packets uploaded to NACC to date. Biofluid samples, including DNA, PBMC, mRNA, plasma and serum on the vast majority of participants, and CSF on a subset, have been collected during the ARTFL/LEFFTDS studies, transferred and processed at the National Centralized Repository for Alzheimer's Disease and Related Dementias. Over 900 MRI scans using a standardized protocol have been performed in 585 participants, and these data have undergone quality control inspection and transferal to the Laboratory of NeuroImaging. All data, samples and scans are available and have been used by investigators within and outside of the ARTFL/LEFFTDS Consortium. The ALLFTD Clinical Core will continue to build on the obvious success of the ARTFL and LEFFTDS protocols by recruiting additional participants in either the longitudinal or biofluid-focused arm. The Clinical Core will enroll and evaluate up to 1100 participants annually in the longitudinal arm, and will include 500 asymptomatic and mildly symptomatic members of kindreds with familial FTLD and 600 mildly symptomatic sporadic FTLD patients. Approximately 1000 additional FTLD patients will be recruited into the biofluid focused arm. In partnership with the FTD Disorders Registry, participants in both arms will be followed remotely, requested to complete questionnaires and provided with periodic updates and information of FTLD research opportunities. The sites in the Clinical Core will provide high quality clinical data, biofluid samples and MRI scans to be integrated for use in all cores and projects, and shared with the scientific community.